Hardeners for photographic processing solutions



" in emulsion layers.

. Diacetyl acetone HARDENERS FOR PHOTOGRAPHIC PROCESSING SOLUTIONS Cyril J. Stand, Rochester, N. Y., and Catherine Salo Popper, Fort Davis, Eastman Kodak Company, corporation of New Jersey Tex, assignors to Rochester, N. Y., a

No Drawing. Application March 25, 1941, Serial No. 385,146

9.Claims.

This invention relates to photographic materials and particularly to hardening photographic gelatin or emulsions by adding certain hardening agents to photographic processing solutions.

The use of hardening agents to prevent the softening or swelling of photographic emulsion layers during processing, particularly at high temperatures, is well known. Hardening agents are equally suitable for use in the emulsion andv in the developer. Patent 2,063,351, diketone hardening In Stand and Briggs U. S.

agents are described-for use Of the diketone compounds described in this patent, we have found that the aromatic diketones are unsuitable for incorporation in developers or prebaths because of incompatibility with the developer or because of lack of hardening action.

It is, therefore, an object of the present invention to provide hardening agents suitable for incorporation in photographic developers or prebaths. Other objects will appear from the following description of our invention.

These objects are accomplished, according to the present invention, by the incorporation of dialkyldiketones in photographic developing solutions or prebaths used to treat the exposed emulsion layer before development.

According to our invention the dialkyldiketone hardener is added to an ordinary photographic developing solution or is made up as a separate solution to treat the exposed emulsion before development. A separate solution of the hardener is preferably made up with a small volume of solvent such as water or methyl alcohol and this solution is then diluted to the desired concentration in the developing solution.

Hardening agents of the which we have found suitable for use in this way are the following:

I Diacetyl Sym.-dicl1lorodiacety1 Cl (EH24: CIElz-CO $1 CHaCOCHa /CO CHaCOCH;

granted December 8, 1936,-

dialkyldiketone class used for this purpose have been incorporated Acetyl acetone CH3IC OCH2C b-cn. Formyl diacetyl methane CHaC 0 Our hardening agents and method have been found especially suitable for, although not limited to, use with the process of multi-color developement described in Mannes, Godowsky and Wilder U. S. Patent 2,252,718, granted August 19,1941. In the process of that application a photographic film having three superposed emulsion layers sensitive to different regions of the visible spectrum thereon, is exposed and developed in a black and white developer, then selectively exposed to the colors to which the layers are sensitive and developed in a color forming developer after each exposure. In this process there is some tendency for the top emulsion layer to soften during the black and white development step and later to peel from the other emulsion layers. Wehave found that by incorporat ing ahardening'agent such as that described in the present application in the first color developer, the softening and peeling of the outer emulsion layer is decreased or overcome. Under the conditions of development used in this processing, that is 10 to 12 minutes at F., diacetyl and other dialkyldiketones were found to be effective in producing sufficient hardness of the top emulsion layer to prevent peeling. This hardening efiect was-produced without interfering with the developing action.

The hardening agents which We employ may be used in amounts ranging from 0.15 to 1.5% by weight of the developing solution, the preferred range being from 0.25 to 0.5%.

The following example of a hardening developer is illustrative: Solution A p-Aminodiethylaniline hydrochloride ams 2 Sodium sulfite do 6 Sodium carbonate do 50 Potassium bromide do 5 Potassium thiocyanate do 1 Diacetyl' dn 1.5 Water to 950 Solution B o-Hydroxydiphenyl grams 3 Sodium hydroxide do 5 Water to 50 (Solution B is added to Solution A.)

The hardening agents which we use result in overcoming the softening of the emulsion layer tion has been found in some cases'to improve the resolving power of emulsions after processing.

Our hardening method may be used not only with sensitive photographic emusions but may also be used to harden non-sensitive photographic gelatin layers, suchas overcoating and backing layers and gelatin layers coated on various supports such as film, paper or cloth.

I It is to be understood that our invention is susceptible of modifications within the scope of the disclosure and claims and that the examples are to be taken as illustrative only.

We claim:

1. The method of hardening a photographic gelatin layer ofan exposed photographic element including a silver halide layer which comprises treating said gelatin layer with a taining a dialkyl diketone.

2. The method of hardening an exposed gela- ,.tino-silver halide emulsion layer which comprises treating said layer with a solution containing a diacetyl.

3. The method of hardening an exposed gelatino-silver halide emulsion layer which comprises treating said layer with a solution containing diacetyl.

solution condialkyl diketone.

4. The method of hardening an exposed gelatino-silver halide emulsion layer which comprises treating said layer with a solution containing symmetricafdichloro diacetyl.

5. The method of hardening an exposed gela tino-silver halide emulsion layer which comprises treating said layer with a solution containing an acetyl acetone. 6; The method of hardening an exposed gelatino-silver halide emulsion layer which comprises treating said layer with a solution containing diacetyl acetone.

'1. The method of hardening an exposed gelatino.-silver halide emulsion layer which comprises developing said layer in a photographic developing solution containing a dialkyl diketone.

8. A hardening photographic developing solution comprising an aqueous solution of a, photographic developer containing a dialkyl diketbne.

9. In the treatment of an exposed multi-layer photographic element having a plurality of differentially-sensitive gelatino-silver halide emulsionlayers on one side of a support, the step of hardening and preventing peeling of the outermost emulsion layer from the underlying emulsion layers, which comprises developing said element in a solution of a developing agent and a CYRIL J L STAUD.. CATHERINE SALO POPPER. 

